Furnace construction with slidable carriage

ABSTRACT

In a sealed-combustion furnace an outer casing is provided with a combustion air intake duct and an exhaust flue both communicating through the wall. A removeable carriage assembly is slidably received in the housing. A sheet metal shell is mounted on the carriage for dividing the interior of the casing into two compartments-one for receiving room air for heating and the other providing the heating chamber. A room air blower, a combustion air blower, a combustion chamber and the heat exchanger are all mounted on the carriage and removeable therewith. The combustion air blower receives outside air from the intake duct and forces it into the combustion chamber.

United States Patent Honaker, Jr.

[451 Aug. 1, 1972 [54] FURNACE CONSTRUCTION WITH SLIDABLE CARRIAGE [72] Inventor: Bernard G. Honaker, Jr., Wichita,

Kans.

[73] Assignee: The Coleman Company, Inc.,

Wichita, Kans.

[22] Filed: Oct. 14, 1970 [21] Appl. N0.: 80,554

[52] US. Cl. ..126/85 B, 126/110 B, 126/116 B [51] Int. Cl ..F24h 3/02 [58] Field of Search....l26/85 R, 85 B, 110 R, 110 B, 126/116 R, 116 B, 307 R, 114, 67; 98/62 2,960,085 ll/1960 Du Fault ..l26/l1O B X 3,274,989 9/1966 Jenson et a]. ..l26/85 B X 3,394,696 7/1968 Cooper ..l26/85 B X 3,446,202 5/1969 Cooper et al. ..l26/85 B X Primary Examiner-Charles .l. Myhre Attorney-Dawson, Tilton, Fallon & Lungmus 5 7] ABSTRACT In a sealed-combustion furnace an outer casing is provided with a combustion air intake duct and an exhaust flue both communicating through the wall. A removeable carriage assembly is slidably received in the housing. A sheet metal shell is mounted on the carriage for dividing the interior of the casing into two compartments-one for receiving room air for heating and the other providing the heating chamber. A room air blower, a combustion air blower, a combustion chamber and the heat exchanger are all mounted on the carriage and removeable therewith. The combustion air blower receives outside air from the intake duct and forces it into the combustion chamber.

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FURNACE CONSTRUCTION WITH SLIDABLE CARRIAGE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sealed-combustion furnaces or space heaters for use in recreational vehicles which include travel trailers, motor homes, and campers mounted on pick-up trucks. These vehicles require heating equipment similar to that used in mobile homes, but which must be specially designed to meet tighter space requirements. Typically, these furnaces or heaters are designed to fit beneath counters; and, hence, they are called undercounter furnaces. The novel features of this invention also have application to other types of wall or space heaters.

2. Known Systems In heaters of this type, in which the combustion chamber and heat exchange units are designed to occupy a very small space, it is desirable to use some means for forcing both the room air being heated and the combustion air that is drawn in. Further, particularly in applications for recreational vehicles, it is desirable to both exhaust the heated combustion gases and draw in the fresh combustion air through a common opening in a vertical wall of the vehicle.

Because of the small opening desired to be formed in the wall of the vehicle, the furnace unit is preferably installed from the inside of the space being heated, and if this is the case, it becomes impossible to gain access to the unit for maintenance and repair from the outside of the vehicle. Further, because the outer casing of the furnace is normally permanently secured to the duct work and to the floor or other walls of the vehicle, it is even difficult to remove the furnace from the inside of the vehicle for maintenance.

SUMMARY OF THE INVENTION In the present inventive system, an undercounter furnace includes an outer housing which is provided with a combustion air inlet and an exhaust outlet both communicating through a common aperture in the wall of the vehicle being heated. A removeable carriage assembly is slidably received in the housing which may be permanently secured to the unit. On the carriage are mounted a room air blower, a combustion air blower, a burner, a heat exchanger and a sheet metal shell which divides the interior of the casing into two compartments one for drawing in room air and the other for housing the burner and heat exchanger for heating the room air and passing it to the distribution system. The combustion air blower receives outside air from the intake duct and forces it into a firebox, also mounted on the carriage. The shell on the carriage provides a heating chamber adapted to receive the heat exchanger.

In servicing the unit, a front panel is removed and the electrical and gas fittings disconnected, and the slidable carriage may be removed through the front of the furnace, including the room air blower, the combustion air blower, the firebox, the heat exchanger, and the shell which forms the two room air compartments.

In a preferred embodiment, the shell which forms the heating chamber is provided with a generally horizontally extending wall as well as two vertically extending side walls which seal with the furnace casing so that the room air being heated may be drawn in above the horizontal wall and fed to a rear room air blower and then passed over the heat exchanger and into the duct work for distributing the heated air.

Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment wherein identical reference numerals will refer to like parts in the various views.

THE DRAWING FIG. 1 is a frontal perspective view of a wall furnace incorporating the present invention;

FIG. 2 is a frontal perspective view showing the sliding carriage removed from the furnace housing;

FIG. 3 is a rear perspective view of the furnace of FIG. 2;

FIG. 4 is a rear perspective view of the furnace of FIG. 1 with certain elements in exploded relation and with a portion of the furnace casing broken away;

FIG. 5 is a side cross sectional view of the fresh air intake and exhaust outlet;

FIG. 6 is a frontal perspective view of the sliding carriage and the elements supported thereby; and

FIGS. 7-9 illustrate typical distribution systems with which the furnace of the present invention may be used.

DETAILED DESCRIPTION Turning first to FIG. 1, an undercounter furnace is seen as including a generally box-shaped outer casing designated by reference numeral 10 including an upper wall 11, first and second side walls 12 and 13, a rear wall 14 (FIG. 3) and a bottom 15 (FIG. 2) all formed into a unitary construction and providing a front opening generally designated 16 in FIG. 2. The front of the casing 10 is adapted to receive a cover plate 17 (FIG. 1) which may be secured to the casing with a conventional latch. To the sides of the casing 10 are welded angle brackets (see the bracket 10a in FIG. 3) for securing the casing in place in a mobile home.

In the embodiment illustrated in FIG. 1, the upper portion of the removable front panel 17 is provided with a louver 18 for the intake of room air to be heated, and schematically designated by the arrows 19 which are intended to pictorially illustrate air flow. The side walls 12 and 13 and the bottom 15 of the casing 10 are provided with knockouts at the locations designated respectively 20, 21 and 22 in FIG. 1 for the distribution of the heated room air, as schematically designated respectively by the flow arrows 20a, 21a, and 22a in FIG. 1. In the illustration, all of the knockouts are removed, but this need not necessarily be the case, as will be evident from a viewing of FIGS. 7-9. That is, normally, the heated room air will flow out of either the bottom knockout or the side knockouts, but not both.

In FIG. 7, the furnace is located beneath a counter and set behind a cover 23 in the front wall of the counter. In this installation, the knockout at location 22 is removed and the heated room air is distributed through a warm air duct system 24 beneath the floor of the vehicle. The room air to be heated is, of course, drawn in through the louver 18 on the cover panel 17 of the casing 10. In the installation of FIG. 8, the knockouts at the side locations 20 and 21 are removed and replaced with connectors for a circular warm air duct system which is located above the floor of the mobile home. In the installation of FIG. 9, the furnace is mounted flush with the vertical wall of the counter, and the front panel of the casing 10 is replaced with a louvered panel 17a which contains louvers 18a and lower side louvers 18b and an access door 18c. In this installation, the room air to be heated is drawn into the upper louvers 18a in panel 17a, and the heated air is returned through the lower side louvers 18b. As will be disclosed more fully below, the room air that is drawn in is separated from the heated air within the furnace by means of a shell which is mounted on a sliding carriage and removeable from the casing 10 along with the room air blower, combustion air blower, firebox, heat exchanger and burner.

It will be observed that in the installations of FIGS. 7-9, the back wall 14 of the casing 10 is adjacent a side wall of the mobile home, designated W and through which the fresh air for combustion and the flue gases pass, as will be explained presently. Turning now to FIG. 5, the wall of the mobile home or other unit being heated is again designated W, and to the exterior of the wall W there is mounted 'a vent hood generally designated 25 and located about a hole 26 formed in the wall W. An aperture in the form of a segmented annulus and designated 27 is formed in the upper portion of the vent hood 25 for exhausting heated flue gases. As best seen in FIGS. 4 and 5, located at the center of the annular exhaust opening 27 is a frusto-conical member 28 having an enlarged base portion of the frustum facing outwardly and with its axis colinear with the axis of an exhaust tube 29 attached to the vent hood 25 by means of a sleeve 30. The larger diameter of the frustum 28 is about equal to or slightly greater than the diameter of the exhaust tube 29 for forcing the heated exhaust gases in a direction indicated by the arrows in FIG. that is, when flow is established by the combustion blower about the frustum a region of relatively low pressure is developed at the larger, outward base. This low pressure region causes the flow to curl back around the frustum so that it does not disperse appreciably toward the sides of the vent hood. This action results in a considerable reduction in the maximum temperature of the wall adjacent the vent hood and assists in preventing recirculation of the combustion products into an inlet air opening 31 formed in the vent hood 25 beneath the exhaust opening 27.

A semicircular baffle 32 is formed about the upper periphery of the fresh air intake aperture 31 and extending outwardly of the vent hood 25 in order to further prevent the recirculation of heated flue gases into the fresh air intake under certain wind conditions. A pocket-shaped member 33 is formed about the interior of the intake aperture 31, and it provides an upper opening as at 34 for receiving the intake combustion air, as schematically indicated-by the arrow 35. The intake air is routed thence through an annular region about the exhaust pipe 29 which serves as a heat exchange medium in cooling the exhaust gases and preheating the fresh combustion air. An oval-shaped extension member 36 extends through the wall aperture 26 from the rear of the vent hood 25 to sealingly receive an outwardly-extending flange of similar cross section designated 37 in FIG. 4 and mounted to the rear of the back wall 14 of the furnace casing 10.

Welded to the inner surface of the back wall 14 of the furnace casing 10 is a sheet metal plate 39 defining an upper circular aperture 40, a generally rectangular aperture 41 and a boot-shaped recess 42 which, when the plate 39 is secured to the back wall 14 forms a fresh air intake conduit. The circular aperture 40 forms a throughput for heated flue gases. The subject matter illustrated in FIGS. 4 and 5 and just described is set forth herein for completeness, and it is reserved for claiming in a copending application of mine which is owned by the same assignee as the present invention and entitled Flue Exhaust and Combustion Air Intake Assembly for Wall Furnace, filed Oct. 14, 1970, Ser. No. 80,605.

A carriage assembly generally designated by reference numeral 45 and best seen in FIGS. 2, 4 and 6 is slidably received within the casing 10, and the carriage assembly 45 includes a sheet metal base plate 46 with upwardly-turned side flanges 47 for guiding the carriage between the side walls 12 and 13 of the casing 10.

Mounted to the top of the base plate 46 is a shell which bears a general designation 50, and it includes an upper hood portion 51, a horizontal separator plate 52 extending forwardly of the hood 51 (see FIG. 2) and first and second vertical side plates 53 and 54 which seal the horizontal plate 52 and lower portion of the hood 51 with the base plate 46 and casing side walls. The function of the shell 50 is to separate the interior of the easing into two compartments for room air one for air drawn in from the room to be heated and the other for heating this air and passing it to the distribution system. That is, the vertical side plates 53 and 54, hood 51, and horizontal separator plate 52 cooperate with the side walls of the casing 10 of the furnace so that room air drawn in through the louver 18 on the front panel 17 passes over the horizontal plate 52, around the top and sides of the hood 51 and down behind the vertical side plates 53 and 54 and into the side openings of a room air blower scroll 55 located beneath and behind the hood 51.

The vertical side plates 53 and 54 are provided with rearwardly-extending flanges 53a (FIG. 6) and 54a (FIG. 1) which are received in grooves suitably formed from sheet metal secured to the interior of the side walls 12 and 13 of the casing 10, and the outer side edges of the horizontal plate 52 slide along ledges which extend inwardly of the side walls 12 and 13 and are located beneath the outer edges of the plate 52 when the carriage assembly is fully inserted. Further, the horizontal plate 52 is provided with tabs 52a and 52b (FIG. 6), each of which are provided with an aperture for receiving a bolt in securing the carriage assembly to a similar tab extending inwardly of the side walls 12 and 13 of the casing 10 for securing the carriage assembly to the casing 10 in its operative condition.

The room air blower scroll 55 is, of course, fitted with a suitable air wheel (not shown) for drawing the room air to be heated and forcing it through a rectangular aperture 56 formed at the rear of the shell 50. Located adjacent the room air scroll 55, but on the opposite side from the motor bracket 57 is a combustion blower scroll 59 which is provided with a rear extension 60 defining a rectangular aperture 61 and a forwardlyextending conduit 62 which feeds into an aperture 63 (see FIG. 6) on the vertical side plate 54 of the shell 50. The extension 60 of the combustion air scroll 59 is sealingly attached to the plate 39 so that the aperture 61 communicates with the combustion air intake duct 42.

A motor is retained by a bracket that is bolted to rubber cushion pads on blower scroll 55. The motor has sides to drive both the room air blower and the combustion air blower. Thus, fresh air for combustion is drawn into the intake aperture 31 on the vent hood 25 and routed above the pocket 33 and into the fresh air intake duct 42 to the blower scroll 59. Thence, the

fresh air is forced through the side plate 54 of the shell 50 and into a combustion chamber (or firebox) 65 which houses a conventional gas burner. See the arrows 66a, 66b and 660 in FIG. 1 representing the flow of inslot 69 is then covered with a cover plate 70 (see FIG.

1) to maintain the sealed separation between room air beingtaken in and heated room air being distributed through the duct system.

Although not shown in the drawing for clarity of illustrating the inventive concept, a conventional heat exchanger is received beneath the hood 51 of the shell 50, and preferably it includes a number of separated chambers extending front-to-rear and communicating with the combustion chamber 65 for routing the combustion gases within the hood 51 to a rear exhaust ex tension tube 75 (see FIG. 4) extending from the rear of the hood 51 and through the circular aperture 40 of the L-shaped plate 39 to telescopically receive the exhaust pipe 29, as previously described. A peripheral sealing gasket 76 seals the passage of the exhaust extension 75 to the aperture 40 to prevent the passage of fresh air intake therethrough. The type of heat exchanger and burner which are preferably used in the inventive furnace are of the general type disclosed in the US. Pat.

- No. 3,394,696 of R. R. Cooper.

' arrows 80a, 80b and 80c in FIG. 1; and the flow of the same 'air through the aperture 56 and into the heating chamber beneath the hood 51 which contains the heat exchange. elements is schematically illustrated by the dashed arrows 81a and 81b in FIG. 1.

Thus, when the electrical and gas connections are disconnected and the tabs 52a and 52b are disconnected from their associated tabs on the casing 10, the entire carriage assembly 45, including the gas burner,

heat exchanger, shell 50, motor, room air scroll 55, and

combustion air scroll 59 may be removed from the housing 10 for repair or maintenance. It is not necessary to disconnect gasket 76 or the gasket around aperture 61 as these seals are formed by compression-fit of the parts and will be disconnected by removal of the carriage.

Having thus described in detail a preferred embodiment of the inventive furnace wherein a carriage assembly is slidably received within an outer casing and easily removed therefrom, persons of ordinary skill in the art will be able to modify certain of the structure which has been disclosed in the illustrated embodiment and to substitute equivalent elements for those which have been described; and it is, therefore, intended that all such modifications and substitutions be covered as they are embraced within the spirit and scope of the appended claims.

I claim:

1. In a sealed combustion furnace for selectively distributing heated room air, the combination comprising an outer casing adapted to be secured to the unit to be heated and provided with combustion air intake means and flue gas exhaust means extending through a wall of the unit, said casing including a removable panel for covering a front opening therein, said panel having room air intake opening means in the upper portion thereof; a carriage assembly removably received in said casing through said front opening; a shell mounted on said. carriage and including a hood centrally placed thereon and having an opening in the lowerfront portion thereof and adapted to receive heat exchange means; vertical side plates extending laterally of said hood adjacent said lower front opening thereof to connect with the respective side of said casing; a separator plate extending forwardly of said hood above said opening and cooperating with said vertical side plates,

said hood and said casing to provide a first and a V second compartment, said second compartment adapted to receive a combustion chamber and said heat exchange means; room air blower means on said carriage assembly for drawing air from the room to be heated through said intake opening means thence over said separator plate and about the exterior of said hood through said first compartment thence forcing it into said second compartment for heating it thence passing it to distribution means communicating with said furnace in a space at least partially defined by said separator plate and said vertical plates; and combustion air blower means on said carriage for receiving air from said air intake means and delivering it to said combustion chamber from which the flue gases are discharged through said flue gas exhaust means.

2. The apparatus of claim 1 wherein said casing is rectilinear in shape and includes a flat bottom and flat side walls, and wherein said carriage assembly includes a flat base plate with upturned side flanges whereby said base plate of said carriage assembly is adapted to slide along the bottom of said casing and said side flanges are guided by the side walls of said casing.

3. The combination of claim 1 wherein said separator plate is generally horizontal and said shell further comprises an upper hood extending above said separator I riage behind said vertical plates and said separator plate and beneath a rear extension of said hood, said shell defining an aperture beneath said hood for the passage of room air from said scroll into a heating chamber partially defined by said hood. 

1. In a sealed combustion furnace for selectively distributing heated room air, the combination comprising an outer casing adapted to be secured to the unit to be heated and provided with combustion air intake means and flue gas exhaust means extending through a wall of the unit, said casing including a removable panel for covering a front opening therein, said panel having room air intake opening means in the upper portion thereof; a carriage assembly removably received in said casing through said front opening; a shell mounted on said carriage and including a hood centrally placed thereon and having an opening in the lower front portion thereof and adapted to receive heat exchange means; vertical side plates extending laterally of said hood adjacent said lower front opening thereof to connect with the respective side of said casing; a separator plate extending forwardly of said hood above said opening and cooperating with said vertical side plates, said hood and said casing to provide a first and a second compartment, said second compartment adapted to receive a combustion chamber and said heat exchange means; room air blower means on said carriage assembly for drawing air from the room to be heated through said intake opening means thence over said separator plate and about the exterior of said hood through said first compartment thence forcing it into said second compartment for heating it thence passing it to distribution means communicating with said furnace in a space at least partially defined by said separator plate and said vertical plates; and combustion air blower means on said carriage for receiving air from said air intake means and delivering it to said combustion chamber from which the flue gases are discharged through said flue gas exhaust means.
 2. The apparatus of claim 1 wherein said casing is rectilinear in shape and includes a flat bottom and flat side walls, and wherein said carriage assembly includes a flat base plate with upturned side flanges whereby said base plate of said carriage assembly is adapted to slide along the bottom of said casing and said side flanges are guided by the side walls of said casing.
 3. The combination of claim 1 wherein said separator plate is generally horizontal and said shell further comprises an upper hood extending above said separator plate for housing a heat exchanger.
 4. The combination of claim 3 wherein said room air blower means includes a scroll mounted on said carriage behind said vertical plates and said separator plate and beneath a rear extension of said hood, said shell defining an aperture beneath said hood for the passage of room air from said scroll into a heating chamber partially defined by said hood. 